NEMATIC, SMECTIC AND COLUMNAR PHASES OF MAIN-CHAIN LIQUID-CRYSTAL POLYETHERS

A number of interesting thermotropic mesophases and transitions occur in main-chain polyethers and copolyethers based on aliphatic spacers a nd various semi-flexible mesogens of the general 1-(4-hydroxyphenyl)-2 -(2-R-4-hydroxyphenyl)ethane (RBPE) or '-hydroxybiphenyl-4-yl)-2-(4-hy droxyphenyl)propane (TPP) type. The unusual effects described here are (i) nematic-nematic transition, (ii) smectic-B (crystal-B) phase and its shear-induced orientation, (iii) calamitic columnar phase, and (iv ) nematic-columnar phase sequence.